Một trong những đặc điểm dân cư – xã hội nổi bật của châu Phi là

A. dân số đông, tăng rất chậm.

B. gia tăng dân số tự nhiên thấp.

C. tỉ lệ nhóm người trên 60 tuổi cao.

D. tuổi thọ trung bình thấp.

Cho hình thang ABCD có hai đáy AB=a , CD= 2a. Gọi M, N là trung điểm AD và BC. Khi đó \(\left|\overrightarrow{MA}+\overrightarrow{MC}-\overrightarrow{MN}\right|\) bằng:

A. \(\dfrac{3a}{2}\)

B. 3a

C. a

D. 2a

Các bạn chỉ cách làm giúp mình với. Cảm ơn !

Doanh thu du lịch (từ khách quốc tế) của Hoa Kì năm 2004 là:

A. 63,4 tỉ USD

B. 74,5 tỉ USD

C. 85,6 tỉ USD

D. 96,7 tỉ USD

Đốt  cháy 11,9 gam hỗn hợp gồm Zn, Al trong khí Cl 2  dư. Sau khi các phản ứng xảy ra hoàn toàn, thu được 40,3 gam hỗn hợp muối. Thể tích khí Cl 2  (đktc) đã tham gia phản ứng là

A, 8,96 lít

B. 6,72 lít

C. 17,92 lít

D. 11,20 lít

Hue, 17 years old: Being able to make a difference in the lives of people is a wonderful thing to me. That's why I take part in volunteer work. I've been a volunteer for over three years. Once or twice a week, usually on weekends, I teach English and Math to poor children in Long Bien district. My friends and I also encourage other people to donate books to them. We also tutor some young children who can't go to school.

Ngan, 13 years old: My family spends one Saturday morning a month collecting rubbish or planting trees in our neighbourhood. We are not forced or paid to do it, but we enjoy it. In our village, most families volunteer to do this once a month. We cook and give food to patients in some hospitals. My parents also donate their blood once or twice a year to help sick people. At the end of each year, people in my village raise money for poor and homeless people. We love helping others.

 Question 6: Ngan's parents encourage people to donate blood to help sick people.

A. True

B. False

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

With a ­­________ of satisfaction on his face, Keith received his degree from the principal.

A. glow

B. beam

C. ray

D. shine

Cho chất béo X có công thức cấu tạo như sau:

Khi cho X tác dụng lần lượt với: dung dịch KOH, t^o; dung dịch Br₂; H₂ (xt: Ni, t^o); O₂. Số trường hợp có phản ứng xảy ra là

A. 1

B. 2 

C. 3 

D. 4 

Mark the letter A,B,C or D on your answer sheet to indicate the word that differs from the rest in the position of the main stress in each of the following questions.

A. necessity

B. aviation

C. confidential

D. supersonic

Read the passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions

Very few people in the modern world obtain their food supply by hunting and gathering in the natural environment surrounding their homes. This method of harvesting from nature’s provision is the oldest known subsistence strategy and has been practiced for at least the last two million years. It was, indeed, the only way to obtain food until rudimentary farming and the domestication of wild animals were introduced about 10,000 years ago.

Because hunter-gatherers have fared poorly in comparison with their agricultural cousins, their numbers have dwindled, and they have been forced to live in marginal environments, such as deserts and arctic wastelands. In higher latitudes, the shorter growing seasons have restricted the availability of plant life. Such conditions have caused a greater dependence on hunting, and on fishing along the coasts and waterways. The abundance of vegetation in the lower latitudes of the tropics, on the other hand, has provided a greater opportunity for gathering a variety of plants. In short, the environmental differences have restricted the diet and have limited possibilities for the development of subsistence societies.

Contemporary hunter-gatherers may help us understand our prehistoric ancestors. We know from the observation of modern hunter- gatherers in both Africa and Alaska that a society based on hunting and gathering must be very mobile. While the entire community camps in a central location, a smaller party harvests the food within a reasonable distance from the camp. When the food in the area has become exhausted, the community moves on to exploit another site. We also notice seasonal migration patterns evolving for most hunter-gatherers, along with a strict division of labor between the sexes. These patterns of behavior may be similar to those practiced by mankind during the Paleolithic Period.

Question 66:The word “conditions” in the second paragraph refers to________.

A.   the places where plenty of animals and fish can be found

B.   the situations in which hunter-gatherers can grow some crops

C.   the environments where it is not favorable for vegetation to grow

D.   the situations in which hunter-gatherers hardly find anything to eat